3 steps for optimal grassweed control in spring barley

EXPERT VIEW

Simple steps can maximise the weed control benefits of spring barley, says Will Smith.

Spring barley is increasingly popular because it provides an opportunity to control grass weeds in the rotation.

But simply growing the crop does not guarantee a lower grassweed burden – especially in fields with large weed populations after what has been a tough couple of years for control in winter crops.

Typically, for example, 15-20% of blackgrass emerges in the spring. Add wild oats, bromes and even annual meadow grass into the mix and there can be a considerable weed burden to deal with.

But all is not lost. The key advantage spring barley offers over winter wheat or barley in managing grass weeds is the additional time it gives to employ all the cultural control measures. Here are three steps to make life easier:

An important part of spring cropping involves taking out all weeds carried over from the autumn before drilling – typically by using glyphosate or tillage.

SFI payments of £129 /ha are available for the CSAM2: Multi-species winter cover crop option. This makes it important to ensure their plans to destroy the cover crop before sowing spring barley comply with Defra’s terms and condiitons.

Whether applying glyphosate, cultivating or crimping the cover crop to destroy it, the critical factor is ensuring it is fully killed off before drilling. Typically, this is four to six weeks before the intended drilling date.

Destroying the cover crop early also opens up the canopy, allowing a flush of weeds and for farmers to see what weeds are already present and act accordingly.

Establishing spring barley well helps the crop compete against grass weeds – as well as giving the best possible chance of above-average yields.

With the drilling window for spring barley stretching from January to May, there may be flexibility with the drilling date, depending on the weather.

Even though earlier drillings are likely to face more black grass, picking the best conditions for establishment is preferable for grass weed control regardless of the calendar date.

If you can drill in good conditions in February and get herbicides on, you will be in a better position than in April with a rough, dry seed bed.

Farmers should consider increasing seed rates on fields with a known grass weed problem to improve crop competition and allow for any potential losses from herbicide applications.

Most farmers know which fields have grass weed issues, especially blackgrass and wild oats. “As soon as weeds are in the crop, they take light nutrients and water – and, in this situation, they should be tackled head-on.

What you want to do is stop them from establishing. You are better off trying to control them pre-emergence. Then there’s still the option of post-emergence herbicides to take out any grass weeds that survive.

Relying on post-emergence chemistry alone only gives one opportunity to control grass weeds. This high-stakes option can leave big yield robbers like wild oats in the field or return a large amount of seed for following crops if blackgrass is not controlled.

When selecting pre-emergence herbicides for spring barley, check the label rates as many popular options are only able to be used at half the winter wheat rate.

A positive for products like Avadex Excel and Avadex Factor (tri-allate) is that the label allows the full rate to be used on spring barley, meaning farmers can expect the high levels of control they are used to from Avadex.

Both products also have approval for use on malting barley, which will be a priority for growers in Scotland and East Anglia. Choosing between Avadex Factor and Avadex Excel largely depends on what equipment is available.

Avadex is highly active against wild oats in particular. In this case, we see very little difference in performance between Avadex Factor and Avadex Excel despite Avadex Factor delivering less tri-allate per hectare.

Applying Avadex pre-emergence to spring barley gives farmers confidence that they have improved the control of all the key spring emerging grass weeds, with bonus activity on problem broad-leaved weeds like speedwell and cleavers.

Will Smith, is UK and Ireland technical lead for crop protection company Gowan. For details, visit www.gowanco.com